/Engine/Source/Runtime/Engine/Public/SceneManagement.h
Allows MIDs being created and released during view rendering without the overhead of creating and releasing objects As MID are not allowed to be parent of MID this gets fixed up by parenting it to the next Material or MIC
[UMaterialInstanceDynamic](API\Runtime\Engine\Materials\UMaterialInstanceDynamic) * GetReusableMID ( class [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * InSource )